Focus ring replacement method and plasma processing system

ABSTRACT

A method performed by a processor of a plasma processing system including a transfer device and a plasma processing apparatus that includes a process chamber. The process chamber includes a mount table on a surface of which a first focus ring is placed. The method includes controlling the transfer device to transfer the first focus ring out of the process chamber without opening the process chamber to the atmosphere; after the first focus ring is transferred out of the process chamber, controlling the plasma processing apparatus to clean the surface of the mount table; and after the surface of the mount table is cleaned, controlling the transfer device to transfer a second focus ring into the process chamber and place the second focus ring on the surface of the mount table without opening the process chamber to the atmosphere.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of U.S. patentapplication Ser. No. 16/594,422 filed on Oct. 7, 2019, which is acontinuation application of U.S. patent application Ser. No. 15/642,517filed on Jul. 6, 2017 (now U.S. Pat. No. 10,490,392), which is based onand claims priority to Japanese Patent Application No. 2016-139681,filed on Jul. 14, 2016, the entire contents of which are incorporatedherein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

An aspect of this disclosure relates to a focus ring replacement methodand a plasma processing system.

2. Description of the Related Art

A known plasma processing apparatus performs plasma processing on asubstrate placed on a mount table disposed in a process chamber. Such aplasma processing apparatus includes consumable parts that graduallywear as a result of repeatedly performing plasma processing (see, forexample, Japanese Laid-Open Patent Publication No. 2006-253541).

One example of a consumable part is a focus ring that is disposed tosurround a substrate placed on the upper surface of the mount table. Thefocus ring is abraded due to exposure to plasma and therefore needs tobe periodically replaced.

In a related-art method, a focus ring is replaced manually by anoperator after opening the process chamber to the atmosphere.

However, with the related-art method where the process chamber is openedto the atmosphere, it takes a long time to replace a focus ring. Also,because it is not possible to process substrates in the process chamberwhile replacing the focus ring, the related-art method reducesproductivity.

SUMMARY OF THE INVENTION

In an aspect of this disclosure, there is provided a method performed bya processor of a plasma processing system including a transfer deviceand a plasma processing apparatus. The plasma processing apparatusincludes a process chamber, and the process chamber includes a mounttable on a surface of which a first focus ring is placed. The methodincludes controlling the transfer device to transfer the first focusring out of the process chamber without opening the process chamber tothe atmosphere; after the first focus ring is transferred out of theprocess chamber, controlling the plasma processing apparatus to cleanthe surface of the mount table; and after the surface of the mount tableis cleaned, controlling the transfer device to transfer a second focusring into the process chamber and place the second focus ring on thesurface of the mount table without opening the process chamber to theatmosphere.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a plasma processing system according toan embodiment;

FIG. 2 is a cross-sectional view of a plasma processing apparatusaccording to an embodiment;

FIG. 3 is a flowchart illustrating a focus ring replacement methodaccording to an embodiment;

FIG. 4 is a drawing illustrating an example of a configuration of aprocess-unit-side transfer device;

FIGS. 5A and 5B are drawings illustrating a pick of a process-unit-sidetransfer device holding a wafer;

FIGS. 6A and 6B are drawings illustrating a pick of a process-unit-sidetransfer device holding a focus ring;

FIG. 7 is a drawing illustrating position detection sensors;

FIGS. 8A and 8B are drawings used to describe a method of correcting theposition of a wafer; and

FIGS. 9A and 9B are drawings used to describe a method of correcting theposition of a focus ring.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention are described below with referenceto the accompanying drawings. In the specification and the drawings ofthe present application, the same reference number is assigned tosubstantially the same components, and repeated descriptions of thosecomponents are omitted.

In a focus ring replacement method according to an embodiment, a focusring is transferred out of a process chamber by a transfer devicewithout opening the process chamber to the atmosphere, the processchamber is cleaned, and another focus ring is transferred into theprocess chamber by the transfer device. A focus ring is disposed in aprocess chamber to surround a substrate placed on the upper surface of amount table, and is used to improve the uniformity of etching.

A focus ring replacement method of the present embodiment can be appliedto various types of plasma processing apparatuses including a focusring.

<Plasma Processing System>

A plasma processing system according to an embodiment is describedbelow. FIG. 1 is a schematic diagram of a plasma processing systemaccording to an embodiment.

As illustrated by FIG. 1 , the plasma processing system is a clustertool including a process unit PU and a transfer unit TU.

The process unit PU performs processes such as a film deposition processand an etching process on substrates such as semiconductor wafers (whichare hereafter referred to as “wafers W”). The process unit PU includesprocess modules PM1 through PM6, a transfer module TM, and load lockmodules LL1 and LL2. The number of process modules PM and the number ofload lock modules LL are not limited to the above examples.

The process modules PM1 through PM6 are connected to the transfer moduleTM and arranged around the transfer module TM. Each of the processmodules PM1 through PM6 performs a process such as a film depositionprocess or an etching process on the wafer W. The process modules PM1through PM6 may be configured to perform the same type of process ordifferent types of processes.

A mount table 3, on which the wafer W is to be placed, is provided ineach of the process modules PM1 through PM6. Also, for example, a purgegas supply system, a process gas supply system, and an evacuation system(not shown) may be provided for the process modules PM1 through PM6.

In each of the process modules PM1 through PM6, a process is performedon the wafer W according to a recipe stored in, for example, a memory ofa controller CU and indicating process steps. Also, for each of theprocess modules PM1 through PM6, a focus ring is replaced atpredetermined timing stored in, for example, a memory of the controllerCU. Details of the process modules PM and the focus ring replacementmethod are described later.

The transfer module TM has a hexagonal shape where a pair of opposingsides are longer than other sides. The process modules PM3 and PM4 areconnected via gate valves G3 and G4 to two short sides of the transfermodule TM at the front end of the transfer module TM. The load lockmodules LL1 and LL2 are connected via gate valves G7 and G8 to two shortsides of the transfer module TM at the rear end of the transfer moduleTM. The process modules PM1 and PM2 are connected via gate valves G1 andG2 to one of two long sides of the transfer module TM. The processmodules PM5 and PM6 are connected via gate valves G5 and G6 to the otherone of the two long sides of the transfer module TM.

The transfer module TM has a function to transfer wafers W and focusrings between the process modules PM1 through PM6 and between theprocess modules PM1 through PM6 and the load lock modules LL1 and LL2(or transfer wafers W and focus rings into and out of those components).For example, a purge gas supply system and an evacuation system (notshown) may be provided for the transfer module TM.

The transfer module TM includes a process-unit-side transfer device TR1that transfers wafers W and focus rings between the process modules PM1through PM6 and the load lock modules LL1 and LL2. Details of theprocess-unit-side transfer device TR1 are described later.

Position detection sensors S11 and S12 are provided at positions thatare near the gate valve G1 of the transfer module TM and on a transferroute along which the wafer W and a focus ring are transferred from thetransfer module TM to the process module PM1. The position detectionsensors S11 and S12 are arranged such that the distance between theposition detection sensors S11 and S12 is less than the outside diameterof the wafer W and the inside diameter of the focus ring. The positiondetection sensors S11 and S12 make it possible to correct the positionsof the wafer W and the focus ring being transferred to the processmodule PM1. Details of the position detection sensors S11 and S12 aredescribed later.

In addition to the position detection sensors S11 and S12, positiondetection sensors S21, S22, S31, S32, S41, S42, S51, S52, S61, and S62are provided at the corresponding positions that are near the gatevalves G2 through G6 of the transfer module TM and on transfer routesalong which wafers W and focus rings are transferred from the transfermodule TM to the process modules PM2 through PM6.

The load lock modules LL1 and LL2 are connected via gate valves G9 andG10 to a transfer module LM. Each of the load lock modules LL1 and LL2has a function to temporarily hold the wafer W transferred from thetransfer module LM and transfer the wafer W to the transfer module TMafter pressure regulation. Also, each of the load lock modules LL1 andLL2 has a function to temporarily hold the wafer W transferred from thetransfer module TM and transfer the wafer W to the transfer module LMafter pressure regulation.

A transfer table, on which the wafer W can be placed, is provided ineach of the load lock modules LL1 and LL2. Also, an evacuation system(not shown) may be provided for the load lock modules LL1 and LL2 topurge, for example, particles of residues and evacuate the load lockmodules LL1 and LL2.

With the process unit PU configured as described above, the pathsbetween the process modules PM1 through PM6 and the transfer module TMand between the transfer module TM and the load lock modules LL1 and LL2can be opened and closed while keeping the process unit PU airtight.Also, the paths between the transfer module LM and the load lock modulesLL1 and LL2 can be opened and closed while keeping the process unit PUairtight.

The transfer unit TU transfers the wafer W between a front openingunified pod (FOUP) described later and the process unit PU, and includesthe transfer module LM.

The transfer module LM has a rectangular shape. Load ports LP1 throughLP3 are provided on one of the long sides of the transfer module LM. AFOUP can be placed on each of the load ports LP1 through LP3. In theexample of FIG. 1 , a FOUP is placed on every one of the load ports LP1through LP3. The FOUP is a container that can house multiple (e.g., 25)wafers W stacked at a constant pitch. The FOUP has an airtight structurethat is filled with, for example, an N₂ gas. In FIG. 1 , FOUPs areconnected via opening-closing doors D1 through D3 to the transfer moduleLM. The number of load ports LP is not limited to the above example.

An aligner AU is provided on one of the short sides of the transfermodule LM. The aligner AU includes a rotary table on which the wafer Wis to be placed, and an optical sensor that optically detects the outeredge of the wafer W. The aligner AU detects an orientation flat or anotch of the wafer W and adjusts the orientation of the wafer W.

The transfer module LM includes a transfer-unit-side transfer device TR2that transfers wafers W and focus rings between the load lock modulesLL1 and LL2, the FOUPs, and the aligner AU. The transfer-unit-sidetransfer device TR2 includes a transfer arm that is attached to a base231 and can be rotated by a rotating mechanism. The transfer-unit-sidetransfer device TR2 can be slid in the longitudinal direction of thetransfer module LM by a sliding mechanism. For example, the transfer armof the transfer-unit-side transfer device TR2 is a double-arm mechanismincluding a pair of multi-joint arms. In the example of FIG. 1 , thetransfer arm includes a first arm 211 and a second arm 221 implementedby multi-joint arms. The first arm 211 and the second arm 221 arearranged vertically and can be extended and retracted.

The sliding mechanism for sliding the transfer-unit-side transfer deviceTR2 includes, for example, a linear motor. More specifically, thetransfer module LM includes a guide rail 232 extending in thelongitudinal direction of the transfer module LM. The base 231 to whichthe transfer arm is attached can slide along the guide rail 232. A moverand a stator are provided on the base 231 and the guide rail 232,respectively. A linear motor driving mechanism 233 for driving thelinear motor is provided at an end of the guide rail 232. The controllerCU is connected to the linear motor driving mechanism 233. The linearmotor driving mechanism 233 is driven according to a control signal fromthe controller CU, and causes the transfer-unit-side transfer device TR2to move together with the base 231 along the guide rail 232 indirections indicated by arrows. The sliding mechanism for driving thetransfer-unit-side transfer device TR2 is not limited to theabove-described example.

A pick 212 is provided at an end of the first arm 211 and a pick 222 isprovided at an end of the second arm 221 so that the transfer-unit-sidetransfer device TR2 can hold two wafers W or two focus rings at a time.With this configuration, the transfer-unit-side transfer device TR2 cantransfer and receive wafers W and focus rings to and from the load lockmodules LL1 and LL2, the FOUPs, and the aligner AU. Thetransfer-unit-side transfer device TR2 may hold and transfer one wafer Wand one focus ring at a time. The number of transfer arms of thetransfer-unit-side transfer device TR2 is not limited to theabove-described example, and the transfer-unit-side transfer device TR2may be implemented as a single-arm mechanism including one arm.

The transfer-unit-side transfer device TR2 also includes a rotationmotor, an extension motor, and an elevation motor (not shown) forrotating, extending, retracting, raising, and lowering the transferarms. Each of the motors is connected to the controller CU, and movesthe transfer arms of the transfer-unit-side transfer device TR2according to a control signal from the controller CU.

Thus, the plasma processing system includes the controller CU thatcontrols components of the plasma processing system such as theprocess-unit-side transfer device TR1, the transfer-unit-side transferdevice TR2, the gate valves G1 through G10, the opening-closing doors D1through D3, and the aligner AU. The controller CU is, for example, acomputer including a central processing unit (CPU) (processor) and amemory storing a program. A focus ring replacement method describedlater may be performed by the processor by executing the program storedin the memory.

<Plasma Processing Apparatus>

A plasma processing apparatus according to an embodiment is describedwith reference to FIG. 2 . FIG. 2 is a cross-sectional view of theplasma processing apparatus. The plasma processing apparatus of FIG. 2can be used as any one of the process modules PM1 through PM6 of theplasma processing system of FIG. 1 .

As illustrated in FIG. 2 , the plasma processing apparatus includes aprocess chamber 10 having a substantially-cylindrical shape. The innerwall of the process chamber 10 may be formed of, for example, anodizedaluminum. The process chamber 10 is grounded.

The process chamber 10 includes a gas shower head 2 for introducing aprocess gas into the process chamber 10. The gas shower head 2 alsofunctions as an upper electrode. A mount table 3 is disposed in theprocess chamber 10 to face the gas shower head 2. The mount table 3 alsofunctions as a lower electrode.

Gas discharge openings 22 are formed in the lower side of the gas showerhead 2 (upper electrode). The gas discharge openings 22 communicate viaa buffer chamber 21 a with a gas supply line 21. From the gas dischargeopenings 22, a process gas is discharged toward a wafer W placed on themount table 3. The gas supply line 21 is connected to a gas supplysystem 23.

The gas supply system 23 includes a supply source that supplies aprocess gas used for a film deposition process performed on the wafer W,and a supply source that supplies a process gas used for an etchingprocess performed on the wafer W. The gas supply system 23 also includesa supply source that supplies a process gas used for a cleaning processof the process chamber 10, and a supply source that supplies a processgas used for a seasoning process of the process chamber 10. The gassupply system 23 includes supply control devices such as valves and flowcontrollers, and can supply process gases into the process chamber 10 atspecified flow rates.

A high-frequency power supply 26 for supplying high-frequency power isconnected via a matching box 25 to the gas shower head 2 (upperelectrode). The gas shower head 2 is insulated by an insulating part 27from the side walls of the process chamber 10.

The mount table 3 includes a body 30 and an electrostatic chuck 31.

The body 30 may be formed of a conductive material such as aluminum. Arefrigerant flow path (not shown) that functions as a temperaturecontrol mechanism is provided in the body 30. The temperature of thewafer W held by the electrostatic chuck 31 is controlled by controllingthe temperature of the refrigerant supplied to the refrigerant flowpath.

The electrostatic chuck 31 is provided on the body 30 and can attractboth the wafer W and a focus ring FR disposed to surround the wafer W. Araised substrate mounting part 32 is formed in the upper center portionof the electrostatic chuck 31. The upper surface of the substratemounting part 32 forms a substrate mounting surface 33 on which thewafer W is to be placed. The upper surface of a lower portion of theelectrostatic chuck 31 surrounding the substrate mounting surface 33forms a focus-ring mounting surface 34.

The electrostatic chuck 31 has a structure formed by sandwiching anelectrode 35 between insulators. The electrode 35 is provided not onlybelow the substrate mounting surface 33 but also below the focus-ringmounting surface 34 so that the electrostatic chuck 31 can attract boththe wafer W and the focus ring FR.

A direct-current power supply 37 is connected via a switch 36 to theelectrode 35 to apply a direct-current voltage to the electrostaticchuck 31. When the direct-current voltage is applied, the electrostaticchuck 31 electrostatically attracts the wafer W and the focus ring FR.As exemplified in FIG. 2 , the substrate mounting part 32 may have adiameter smaller than the diameter of the wafer W so that the outer edgeof the wafer W placed on the substrate mounting part 32 protrudes overthe edge of the substrate mounting part 32.

A heat-transfer-gas supply system 38 is provided for the mount table 3to supply heat-transfer gases (e.g., a helium (He) gas) separately tothe back side of the wafer W and the back side of the focus ring FR.

The heat-transfer-gas supply system 38 includes a firstheat-transfer-gas supply part 38 a that supplies a first heat-transfergas to the back side of the wafer W placed on the substrate mountingsurface 33 and a second heat-transfer-gas supply part 38 b that suppliesa second heat-transfer gas to the back side of the focus ring FR placedon the focus-ring mounting surface 34.

The focus ring FR is placed on the electrostatic chuck 31. A step isformed in the upper side of the focus ring FR such that the outercircumferential part of the focus ring FR becomes higher than the innercircumferential part of the focus ring FR. Also, the innercircumferential part of the focus ring FR is configured to enter a spacebelow the outer edge of the wafer W protruding over the edge of thesubstrate mounting part 32. Thus, the inside diameter of the focus ringFR is smaller than the outside diameter of the wafer W. Thisconfiguration makes it possible to protect the electrostatic chuck 31from plasma during an etching process performed on the wafer W.

A high-frequency power supply 40 for supplying bias power is connectedvia a matching box 39 to the mount table 3. Also, elevating pins (notshown) are provided in the mount table 3. The elevating pins are used topass and receive the wafer W and the focus ring FR to and from theprocess-unit-side transfer device TR1 illustrated in FIG. 1 . Whenpassing the focus ring FR to the process-unit-side transfer device TR1,the elevating pins are raised to lift the focus ring FR from the mounttable 3.

An opening 13 is formed in the side wall of the process chamber 10, anda gate valve G1 is provided to open and close the opening 13. The waferW and the focus ring FR are transferred through the opening 13.

A detachable deposit shield 41 is provided on the inner wall of theprocess chamber 10. The deposit shield 41 is also provided on the outersurface of the mount table 3. The deposit shield 41 prevents a reactionproduct of an etching process from adhering to the inner wall of theprocess chamber 10, and is formed, for example, by coating aluminum withceramic such as Y₂O₃.

A baffle plate 42 having a large number of exhaust holes is providedaround the mount table 3 to uniformly evacuate the process chamber 10.The baffle plate 42 is formed, for example, by coating aluminum withceramic such as Y₂O₃. A vacuum pump 12 such as a turbo molecular pump ora dry pump is connected to an evacuation pipe 11 below the baffle plate42. The plasma processing apparatus includes a controller 50 forcontrolling other components of the plasma processing apparatus. Thecontroller 50 is, for example, a computer including a central processingunit (CPU) and a program. The program includes, for example, steps(instructions) for controlling the supply of gases from the gas supplysystem 23 and the supply of power from the high-frequency power supplies26 and 40 to perform processes such as a film deposition process and anetching process on the wafer W. The program may be stored in a storagemedium such as a hard disk drive, a compact disk, or a memory card, andinstalled from the storage medium into the computer.

<Focus Ring Replacement Method>

A focus ring replacement method according to an embodiment is describedwith reference to FIG. 3 . FIG. 3 is a flowchart illustrating a focusring replacement method according to an embodiment.

In the example below, it is assumed that the focus ring FR on the mounttable 3 of the process module PM1 is replaced. More specifically, it isassumed that a used focus ring is carried out of the process module PM1and placed in the FOUP, and an unused focus ring placed beforehand inthe FOUP is installed in the process module PM1. Focus rings FR on themount tables 3 of the process modules PM2 through PM6 may also bereplaced according to the focus ring replacement method described below.The focus ring replacement method of the present embodiment is performedby the controller CU by controlling the components of the plasmaprocessing system.

As illustrated by FIG. 3 , the focus ring replacement method of thepresent embodiment includes a wear level assessment step S10, areplacement feasibility determination step S20, a first cleaning stepS30, a carry-out step S40, a second cleaning step S50, a carry-in stepS60, and a seasoning step S70. Each of the steps is described below.

The wear level assessment step S10 is performed to determine whether thefocus ring FR on the mount table 3 of the process module PM1 needs to bereplaced. At the wear level assessment step S10, the controller CUdetermines whether the focus ring FR on the mount table 3 of the processmodule PM1 needs to be replaced. More specifically, the controller CUdetermines whether the focus ring FR needs to be replaced based on oneor more of criteria such as a total RF time, a total RF power, and atotal specific-step value. The total RF time indicates a total amount oftime for which high-frequency power is supplied to the process modulePM1 to perform plasma processing. The total RF power indicates a totalamount of high-frequency power supplied to the process module PM1 toperform plasma processing. The total specific-step value indicates, forexample, a total amount of time for which high-frequency power issupplied to perform a specific step(s) or a total amount ofhigh-frequency power that is supplied to perform the specific step(s).The specific step indicates a type of step in a recipe that is performedin the process module PM1 and causes abrasion of the focus ring FR. Thecalculations of the total RF time, the total RF power, and the totalspecific-step value are started, for example, when the process modulePM1 is installed, when maintenance of the process module PM1 isperformed, or when the focus ring FR is replaced.

For example, when the total RF time is used as a criterion, thecontroller CU determines that the focus ring FR needs to be replacedwhen the total RF time reaches a threshold. In contrast, the controllerCU determines that replacement of the focus ring RF is not necessarywhen the total RF time is less than the threshold. The threshold may bedetermined by, for example, according to a result of an experimentperformed for each type or material of the focus ring FR.

When the total RF power is used as a criterion, the controller CUdetermines that the focus ring FR needs to be replaced when the total RFpower reaches a threshold. In contrast, the controller CU determinesthat replacement of the focus ring RF is not necessary when the total RFpower is less than the threshold. The threshold may be determined by,for example, according to a result of an experiment performed for eachtype or material of the focus ring FR.

When the total specific-step value is used as a criterion, thecontroller CU determines that the focus ring FR needs to be replacedwhen the total RF time or the total RF power for the specific stepreaches a threshold. In contrast, the controller CU determines thatreplacement of the focus ring RF is not necessary when the total RF timeor the total RF power for the specific step is less than the threshold.When the total specific-step value is used as a criterion, the timing ofreplacing the focus ring FR is calculated based on a value related to astep in a recipe where high-frequency power is applied and the focusring FR is abraded. This makes it possible to accurately calculate thetiming of replacing the focus ring FR. The threshold may be determinedby, for example, according to a result of an experiment performed foreach type or material of the focus ring FR.

When it is determined, at the wear level assessment step S10, that thefocus ring FR on the mount table 3 of the process module PM1 needs to bereplaced, the controller CU performs the replacement feasibilitydetermination step S20. When it is determined, at the wear levelassessment step S10, that the focus ring FR on the mount table 3 of theprocess module PM1 does not need to be replaced, the controller CUperforms repeats the wear level assessment step S10.

The replacement feasibility determination step S20 is performed todetermine whether the plasm processing system is in a state where thereplacement of the focus ring FR can be performed. At the replacementfeasibility determination step S20, the controller CU determines whetherthe plasm processing system is in a state where the replacement of thefocus ring FR can be performed. For example, the controller CUdetermines that the replacement of the focus ring FR in the processmodule PM1 can be performed when the wafer W is not being processed inthe process module PM1. In contrast, the controller CU determines thatthe replacement of the focus ring RF cannot be performed when the waferW is being processed in the process module PM1. Also, the controller CUmay be configured to determine that the replacement of the focus ring FRin the process module PM1 can be performed when the processing of wafersW in the same lot as the wafer W being processed in the process modulePM1 is completed. In this case, the controller CU determines that thereplacement of the focus ring FR cannot be performed until theprocessing of wafers W in the same lot as the wafer W being processed inthe process module PM1 is completed.

When it is determined, at the replacement feasibility determination stepS20, that the plasm processing system is in a state where thereplacement of the focus ring FR can be performed, the controller CUperforms the first cleaning step S30. When it is determined, at thereplacement feasibility determination step S20, that the plasmprocessing system is in a state where the replacement of the focus ringFR cannot be performed, the controller CU repeats the replacementfeasibility determination step S20.

The first cleaning step S30 is performed to clean the process modulePM1. At the first cleaning step S30, the control unit CU performs acleaning process on the process module PM1 by controlling the gas supplysystem, the evacuation system, and the power supply system. In thecleaning process, deposits generated by plasma processing in the processmodule PM1 are removed using, for example, plasma of a process gas tomaintain the inside of the process module PM1 in a clean state.Performing the first cleaning step S30 makes it possible to preventdeposits in the process chamber 10 from being stirred up when the focusring FR is transferred from the mount table 3 at the carry-out step S40.Examples of process gases include an oxygen (O₂) gas, a fluorocarbon(CF) gas, a nitrogen (N₂) gas, an argon (Ar) gas, a helium (He) gas, anda mixed gas of two or more of these gases. Depending on processconditions, a dummy wafer W may be placed on the electrostatic chuck 31of the mount table 3 during the cleaning process of the process modulePM1 to protect the electrostatic chuck 31. When no deposit is present inthe process chamber 10 and is likely to be stirred up, the firstcleaning step S30 may be omitted. When the focus ring FR is beingattracted to the mount table 3 by the electrostatic chuck 31, adiselectrification process is performed before the carry-out step S40.

The carry-out step S40 is performed to transfer the focus ring FR out ofthe process module PM1 without opening the process module PM1 to theatmosphere. At the carry-out step S40, the controller CU controls thecomponents of the plasma processing system to transfer the focus ring FRout of the process module PM1 without opening the process module PM1 tothe atmosphere. More specifically, the controller CU opens the gatevalve G1, and controls the process-unit-side transfer device TR1 totransfer the focus ring FR on the mount table 3 of the process modulePM1 out of the process module PM1. Next, the controller CU opens thegate valve G8, and controls the process-unit-side transfer device TR1 toplace the focus ring FR transferred out of the process module PM1 on thetransfer table in the load lock module LL2. Next, the controller CUcloses the gate valve G8, regulates the pressure in the load lock moduleLL2, opens the gate valve G10, and controls the transfer-unit-sidetransfer device TR2 to transfer the focus ring FR from the transfertable to the transfer module LM. Then, the controller CU opens theopening-closing door D3, and controls the transfer-unit-side transferdevice TR2 to place the focus ring FR in the FOUP placed on the loadport LP3.

The second cleaning step S50 is performed to clean the surface (thefocus-ring mounting surface 34) of the mount table 3 of the processmodule PM1 on which the focus ring FR is placed. At the second cleaningstep S50, the control unit CU performs a cleaning process on the surfaceof the mount table 3 of the process module PM1 on which the focus ringFR is placed by controlling the gas supply system, the evacuationsystem, and the power supply system. The cleaning process in the secondcleaning step S50 may be performed in a manner similar to the cleaningprocess in the first cleaning step S30. That is, the cleaning process inthe second cleaning step S50 may be performed using a process gas suchas an oxygen (O₂) gas, a fluorocarbon (CF) gas, a nitrogen (N₂) gas, anargon (Ar) gas, a helium (He) gas, or a mixed gas of two or more ofthese gases. Also, depending on process conditions, a dummy wafer W maybe placed on the electrostatic chuck 31 of the mount table 3 during thecleaning process of the process module PM1 to protect the electrostaticchuck 31.

The carry-in step S60 is performed to transfer the focus ring FR intothe process module PM1 and place the focus ring FR on the mount table 3without opening the process module PM1 to the atmosphere. At thecarry-in step S60, the controller CU controls the components of theplasma processing system to transfer the focus ring FR into the processmodule PM1 without opening the process module PM1 to the atmosphere.More specifically, the controller CU opens the opening-closing door D3,and controls the transfer-unit-side transfer device TR2 to transfer anunused focus ring FR out of the FOUP placed on the load port LP3. Next,the controller CU opens the gate valve G9, and controls thetransfer-unit-side transfer device TR2 to place the unused focus ring FRon the transfer table in the load lock module LL1. Then, the controllerCU opens the gate valve G7 and the gate valve G1, and controls theprocess-unit-side transfer device TR1 to transfer the unused focus ringFR from the transfer table in the load lock module LL1 into the processmodule PM1 and place the unused focus ring FR on the mount table 3.

The seasoning step S70 is performed to season the process module PM1. Atthe seasoning step S70, the control unit CU performs a seasoning processon the process module PM1 by controlling the gas supply system, theevacuation system, and the power supply system. In the seasoningprocess, predetermined plasma processing is performed to stabilize thetemperature and the state of deposits in the process module PM1. Also inthe seasoning step S70, after the seasoning process is performed on theprocess module PM1, a quality-control wafer may be placed in the processmodule PM1 and a predetermined process may be performed on thequality-control wafer. This makes it possible to determine whether theprocess module PM1 is in a normal state.

The focus ring FR can be replaced through the steps described above.

As described above, in the focus ring replacement method of the presentembodiment, the focus ring FR is transferred out of the process chamber10 by using the process-unit-side transfer device TR1, the processchamber 10 is cleaned, and an unused focus ring FR is transferred intothe process chamber 10 by using the process-unit-side transfer deviceTR1 without opening the process chamber 10 to the atmosphere. Thismethod eliminates the need for an operator to manually replace the focusring FR. This in turn makes it possible to reduce the time necessary toreplace the focus ring FR and improves the productivity. Also in thefocus ring replacement method of the present embodiment, the focus-ringmounting surface 34 is cleaned before the focus ring FR is transferredinto the process chamber 10. This makes it possible to prevent depositsfrom being placed between the focus ring FR and the focus-ring mountingsurface 34. This in turn makes it possible to improve contact betweenthe focus ring FR and the focus-ring mounting surface 34, and therebymakes it possible to better control the temperature of the focus ringFR.

<Process-Unit-Side Transfer Device>

Next, an example of a configuration of the process-unit-side transferdevice TR1 is described with reference to FIG. 4 . FIG. 4 is a drawingillustrating an example of a configuration of the process-unit-sidetransfer device TR1.

First, a sliding mechanism of the process-unit-side transfer device TR1is described. As illustrated in FIG. 4 , transfer arms (a first arm 111and a second arm 121) of the process-unit-side transfer device TR1 areattached to a base 131. The base 131 is slidable on guide rails 132 aand 132 b in a Y-axis direction (the longitudinal direction of thetransfer module TM). For example, a ball screw 134 driven by a Y-axismotor 133 is attached to the base 131. The sliding movement of thetransfer arms of the process-unit-side transfer device TR1 can becontrolled by controlling the Y-axis motor 133.

Next, a rotating mechanism of the process-unit-side transfer device TR1is described. As illustrated in FIG. 4 , the transfer arms (the firstarm 111 and the second arm 121) of the process-unit-side transfer deviceTR1 are attached via a rotary plate 135 to the base 131. The rotaryplate 135 is rotatable in the direction of a θ axis that is a rotationalaxis. For example, the rotary plate 135 is rotated by a θ-axis motor 136provided on the base 131. The rotational movement of the transfer armsof the process-unit-side transfer device TR1 can be controlled bycontrolling the θ-axis motor 136.

A pick 112 is provided at an end of the first arm 111, and a pick 122 isprovided at an end of the second arm 121 so that the process-unit-sidetransfer device TR1 can hold two wafers W or two focus rings FR at atime. With this configuration, the process-unit-side transfer device TR1can transfer and receive wafers W and focus rings FR to and from theprocess modules PM1 through PM6 and the load lock modules LL1 and LL2.The number of transfer arms of the process-unit-side transfer device TR1is not limited to the above-described example, and the process-unit-sidetransfer device TR1 may be implemented as a single-arm mechanismincluding one arm.

The process-unit-side transfer device TR1 also includes an extensionmotor (not shown) for extending and retracting the transfer arms. Forexample, the extension motor is provided below the θ-axis motor 136, andis controllable separately from the θ-axis motor 136. Theprocess-unit-side transfer device TR1 may further include an elevationmotor (not shown) for raising and lowering the transfer arms.

Each of the motors including the θ-axis motor 136 and the Y-axis motor133 for driving the process-unit-side transfer device TR1 is connectedto the controller CU, and is driven according to a command from thecontroller CU.

As illustrated in FIG. 1 , a flexible arm 137 is connected to the base131 of the process-unit-side transfer device TR1. Wires for the motorssuch as θ-axis motor 136 pass through the flexible arm 137. The flexiblearm 137 may be implemented by, for example, a tubular arm mechanism. Theflexible arm 137 is hermetically connected to the base 131, and theinside of the flexible arm 137 communicates with the atmosphere via ahole formed in the bottom of the transfer module TM. With thisconfiguration, even when the inside of the transfer module TM is at avacuum pressure, the inside of the flexible arm 137 is at theatmospheric pressure. Accordingly, this configuration makes it possibleto prevent the wires in the flexible arm 137 from being damaged.

As described above, the process-unit-side transfer device TR1 can beslid along the guide rails 132 a and 132 b, and the transfer arms of theprocess-unit-side transfer device TR1 can be extended and retracted.With this configuration, the process-unit-side transfer device TR1 cantransfer wafers W and focus rings FR between the process modules PM1through PM6 and the load lock modules LL1 and LL2.

Next, an example of the pick 112 of the process-unit-side transferdevice TR1 is described. FIGS. 5A and 5B are drawings illustrating thepick 112 holding the wafer W. FIG. 5A is a side view of the pick 112holding the wafer W, and FIG. 5B is a top view of the pick 112 holdingthe wafer W. FIGS. 6A and 6B are drawings illustrating the pick 112holding the focus ring FR. FIG. 6A is a side view of the pick 112holding the focus ring FR, and FIG. 6B is a top view of the pick 112holding the focus ring FR. Although the pick 112 is described below withreference to FIGS. 5A through 6B, the pick 122 may have substantiallythe same configuration.

As illustrated in FIGS. 5A and 5B, multiple (e.g., three) protrusions113 for holding the outer edge of the wafer W are formed on the pick112. The protrusions 113 have, for example, a truncated-cone shape andare arranged to be positioned along the outer edge of the wafer W. Atapered part 114 (or a sloping part) of the truncated-cone shape of eachof the protrusions 13 contacts the outer edge of the wafer W to preventmisalignment of the wafer W with the pick 112. The protrusions 113 maybe formed of, for example, elastomer.

Also, as illustrated in FIGS. 6A and 6B, an upper surface 115 of thetruncated-cone shape of each of the protrusions 113 contacts the lowersurface of the focus ring FR to hold the focus ring FR. This is becausethe inside diameter of the focus ring FR is smaller than the outsidediameter of the wafer W. Thus, the pick 112 of the process-unit-sidetransfer device TR1 can hold the wafer W and the focus ring FR.

As described above, the pick 112 holds the wafer W with the taperedparts 114 of the protrusions 113, and hold the focus ring FR with theupper surfaces 115 of the protrusions 113. This configuration makes itpossible to hold the focus ring FR with the pick 112 without increasingthe length of the pick 112. This in turn makes it possible to preventthe tip of the pick 112 from contacting other parts (e.g., the innerwall of the FOUP) when transferring the wafer W and the focus ring FR.In the example of FIGS. 5A through 6B, the number of the protrusions 113is three. However, the number of the protrusions 113 is not limited tothree.

The process-unit-side transfer device TR1 is preferably configured torotate with the minimum radius of rotation when holding the focus ringFR. This configuration makes it possible to prevent the focus ring FRheld on the pick 112 from contacting other parts. Also, even in a casewhere the wafer W is held on the pick 112, the focus ring FR is held onthe pick 122, and the picks 112 and 122 rotate on substantially the sameplane, this configuration makes it possible to prevent the wafer W andthe focus ring FR from contacting each other.

<Position Detection Sensors>

Next, examples of position detection sensors are described withreference to FIG. 7 . FIG. 7 is a cross-sectional view of a part of theplasma processing system taken along a dashed-dotted line 1A-1B of FIG.1 .

As illustrated in FIG. 7 , the position detection sensor S11 includes alight-emitting part 310 and a light-receiving part 320. Thelight-emitting part 310 is provided in an upper wall 330 of the transfermodule TM, and the light-receiving part 320 is provided in a lower wall340 of the transfer module TM. The light-emitting part 310 emits a laserbeam L toward the light-receiving part 320. The light-receiving part 320detects the laser beam L emitted from the light-emitting part 310.Although FIG. 7 illustrates only the light-emitting part 310 and thelight-receiving part 320 of the position detection sensor S11 as anexample, the position detection sensor S12 also has a similarconfiguration and includes a light-emitting part and a light-receivingpart. The laser beam L emitted from the light-emitting part 310 towardthe light-receiving part 320 of the position detection sensor S11 isblocked for a given period of time by the wafer W or the focus ring FRthat is transferred from the transfer module TM into the process modulePM1. Similarly, the laser beam L emitted from the light-emitting parttoward the light-receiving part of the position detection sensor S12 isblocked for a given period of time by the wafer W or the focus ring FRthat is transferred from the transfer module TM into the process modulePM1.

Next, a method for correcting the positions of the wafer W and the focusring FR is described.

According to an embodiment, the controller CU corrects the position ofthe wafer W and the position of the focus ring FR using the sameposition detection sensors.

First, a case where the wafer W is transferred from the transfer moduleTM to the process module PM1 is described with reference to FIGS. 8A and8B. FIGS. 8A and 8B are drawings used to describe a method of correctingthe position of the wafer W. FIG. 8A illustrates a positionalrelationship between the wafer W and the position detection sensors S11and S12. FIG. 8B is a graph illustrating changes in the sensor outputsof the position detection sensors S11 and S12 while the wafer W istransferred from a position P11 to a position P14 in FIG. 8A. In FIG.8B, t11 indicates a time at the position P11, t12 indicates a time at aposition P12, t13 indicates a time at a position P13, and t14 indicatesa time at the position P14.

The controller CU calculates the amount of misalignment of the wafer Won the pick 112 from a predetermined reference position based on theposition of the wafer W detected by the position detection sensors S11and S12. Next, the controller CU controls the process-unit-side transferdevice TR1 to place the wafer W on the mount table 3 of the processmodule PM1 such that the calculated amount of misalignment is corrected.This method makes it possible to place the wafer W in a predeterminedposition on the mount table 3 of the process module PM1 even when theposition of the wafer W on the pick 112 is misaligned with the referenceposition.

The position of the wafer W on the pick 112 can be calculated based onchanges in the sensor outputs of the position detection sensors S11 andS12 that are caused when the outer edge of the wafer W passes theposition detection sensors S11 and S12. For example, when the wafer W istransferred from the position P11 to the position P14 as illustrated inFIG. 8A, the position of the wafer W on the pick 112 can be calculatedbased on a time period T1 between the time t12 and the time t13corresponding to the position P12 and the position P13 where the emittedlight of the position detection sensors S11 and S12 is blocked by thewafer W. In the example of FIG. 8B, the time period T1 can be calculatedby T1=t13−t12 based on the time t12 at the position P12 and the time t13at the position P13. In FIGS. 8A and 8B, it is assumed that the emittedlight of the position detection sensor S11 and the emitted light of theposition detection sensor S12 are blocked at the same position. However,the emitted light of the position detection sensor S11 and the emittedlight of the position detection sensor S12 may be blocked at differentpositions.

The reference position may be calculated based on, for example, theencoder positions of the rotation motor and the extension motor fordriving the first arm 111 of the process-unit-side transfer device TR1.The reference position may also be calculated according to any otherappropriate method.

Next, a case where the focus ring FR is transferred from the transfermodule TM to the process module PM1 is described with reference to FIGS.9A and 9B. FIGS. 9A and 9B are drawings illustrating a method ofcorrecting the position of the focus ring FR. FIG. 9A illustrates apositional relationship between the focus ring FR and the positiondetection sensors S11 and S12. FIG. 9B is a graph illustrating changesin the sensor outputs of the position detection sensors S11 and S12while the focus ring FR is transferred from a position P21 to a positionP24 in FIG. 9A. In FIG. 9B, t21 indicates a time at the position P21,t22 indicates a time at a position P22, t23 indicates a time at aposition P23, and t24 indicates a time at the position P24.

The controller CU calculates the amount of misalignment of the focusring FR on the pick 112 from a predetermined reference position based onthe position of the focus ring FR detected by the position detectionsensors S11 and S12. Next, the controller CU controls theprocess-unit-side transfer device TR1 to place the focus ring FR on themount table 3 of the process module PM1 such that the calculated amountof misalignment is corrected. This method makes it possible to place thefocus ring FR in a predetermined position on the mount table 3 of theprocess module PM1 even when the position of the focus ring FR on thepick 112 is misaligned with the reference position.

The position of the focus ring FR on the pick 112 can be calculatedbased on changes in the sensor outputs of the position detection sensorsS11 and S12 that are caused when the inner edge of the focus ring FRpasses the position detection sensors S11 and S12. For example, when thefocus ring FR is transferred from the position P21 to the position P24as illustrated in FIG. 9A, the position of the focus ring FR on the pick112 can be calculated based on a time period T2 between the time t22 andthe time t23 taken to transfer the focus ring FR from the position P22to the position P23. At the position P22, the sensor outputs of theposition detection sensors S11 and S12 change from a low (L) level to ahigh (H) level. At the position P23, the sensor outputs of the positiondetection sensors S11 and S12 change from the high (H) level to the low(L) level. In the example of FIG. 9B, the time period T2 can becalculated by T2=t23−t22 based on the time t22 at the position P22 andthe time t23 at the position P23. In FIGS. 9A and 9B, it is assumed thatthe emitted light of the position detection sensor S11 and the emittedlight of the position detection sensor S12 are blocked at the sameposition. However, the emitted light of the position detection sensorS11 and the emitted light of the position detection sensor S12 may beblocked at different positions.

Here, when the focus ring FR is damaged or falls off the pick 112 whilebeing transferred, the waveform of FIG. 9B is not detected. In thiscase, the controller CU determines that an error has occurred during thetransfer of the focus ring FR and terminates the transfer process.

The reference position may be calculated based on, for example, theencoder positions of the rotation motor and the extension motor fordriving the first arm 111 of the process-unit-side transfer device TR1.The reference position may also be calculated according to any otherappropriate method.

A focus ring replacement method and a plasma processing system accordingto the embodiments of the present invention are described above.However, the present invention is not limited to the specificallydisclosed embodiments, and variations and modifications may be madewithout departing from the scope of the present invention.

Although cleaning processes are performed using plasma at the firstcleaning step S30 and the second cleaning step S50 described above, thepresent invention is not limited to this embodiment. For example, thecleaning processes may be performed by non-plasma particle cleaning(NPPC) where particles are removed from components in a process chamberand discharged from the process chamber using a gas impact, a gasviscous force, and an electromagnetic stress instead of plasma.

An aspect of this disclosure provides a focus ring replacement methodand a plasma processing system that can improve productivity.

What is claimed is:
 1. A system, comprising: a transfer module; atransfer device disposed within the transfer module, the transfer devicehaving a transfer arm, a pick that holds objects for the transfer arm,and a motor that drives a motion of the transfer arm; a plasmaprocessing apparatus that includes a process chamber; a positiondetection sensor; and a controller configured to control the transferdevice to transfer a focus ring held by the pick from the transfermodule to a station within a vacuum environment, detect the position ofthe focus ring by the position detection sensor, calculate an amount ofmisalignment of the focus ring on the pick based on the position of thefocus ring detected by the position detection sensors, correct analignment of the focus ring in the station based on the calculatedmisalignment, and place the focus ring at a target location in thestation based on the corrected alignment.
 2. The system of claim 1,wherein the process chamber includes a support at the target location inthe station that has one or more surfaces being configured to support asubstrate and/or the focus ring.
 3. The system of claim 1, wherein thesystem further comprises a gate valve connecting the process chamber andthe transfer module, and the controller is further configured to placethe focus ring in the station based on the detected position withoutopening the process chamber to the atmosphere.
 4. The system of claim 3,wherein the controller is further configured to control the transferdevice to transfer the focus ring out of the process chamber withoutopening the process chamber to atmosphere.
 5. The system of claim 1,wherein the focus ring includes an inner edge defining a circumferenceof an opening formed in the focus ring; and the controller is furtherconfigured to detect the position of the focus ring based on a detectionof the inner edge of the focus ring by the position detection sensor. 6.The system of claim 1, wherein the controller is configured to calculatean amount of misalignment of the focus ring on the pick from apredetermined reference position based on the position of the focus ringdetected by the position detection sensors.
 7. The system of claim 1,wherein the controller is configured to detect a position of the focusring held on the transfer device at or near the gate valve.
 8. Thesystem of claim 1, wherein the controller is configured to calculate theposition of the focus ring on the pick based on changes in the sensoroutputs of the position detection sensors while the focus ring is movedtoward the station.
 9. A method, comprising: controlling a transferdevice holding a focus ring by a pick to transfer the focus ring from aprocess chamber of a plasma processing apparatus to a station within avacuum environment; detecting the position of the focus ring by aposition detection sensor; calculating, with a processor, an amount ofmisalignment of the focus ring on the pick based on the position of thefocus ring detected by the position detection sensors; and correcting analignment of the focus ring in the station based on the calculatedmisalignment; and placing the focus ring at a target location in thestation based on the corrected alignment.
 10. The method of claim 9further comprising: placing the focus ring in the station based on thedetected position without opening the process chamber to the atmosphere.11. The method of claim 10 further comprising: controlling the transferdevice to transfer the focus ring out of the process chamber withoutopening the process chamber to atmosphere.
 12. The method of claim 9,wherein the focus ring includes an inner edge defining a circumferenceof an opening formed in the focus ring; and the method furthercomprising detecting the position of the focus ring based on a detectionof the inner edge of the focus ring by the position detection sensor.13. The method of claim 12 further comprising: calculating an amount ofmisalignment of the focus ring on the pick from a predeterminedreference position based on the detected position of the focus ring. 14.The method of claim 9 further comprising: calculating the position ofthe focus ring on the pick based on changes in the sensor outputs of theposition detection sensors while the focus ring is moved toward the. 15.A non-transitory computer readable medium having instructions storedtherein, that upon execution by a computer, configure the computer toimplement operations comprising: control a transfer device holding afocus ring by a pick to transfer the focus ring from a process chamberof a plasma processing apparatus to a station within a vacuumenvironment, detect the position of the focus ring by a positiondetection sensor, calculate an amount of misalignment of the focus ringon the pick based on the position of the focus ring detected by theposition detection sensors, and correct an alignment of the focus ringin the station based on the calculated misalignment, and place the focusring at a target location in the station based on the correctedalignment.
 16. The non-transitory computer readable medium of claim 15,which upon execution by the computer, further cause the computer toimplement operations comprising: place the focus ring in the stationbased on the detected position without opening the process chamber tothe atmosphere.
 17. The non-transitory computer readable medium of claim16, which upon execution by the computer, further cause the computer toimplement operations comprising: control the transfer device to transferthe focus ring out of the process chamber without opening the processchamber to atmosphere.
 18. The non-transitory computer readable mediumof claim 15, which upon execution by the computer, further cause thecomputer to implement operations comprising: detect the position of thefocus ring based on a detection of an inner edge of the focus ring bythe position detection sensor, wherein the inner edge defines acircumference of an opening formed in the focus ring.
 19. Thenon-transitory computer readable medium of claim 18, which uponexecution by the computer, further cause the computer to implementoperations comprising: calculate an amount of misalignment of the focusring on the pick from a predetermined reference position based on thedetected position of the focus ring.
 20. The non-transitory computerreadable medium of claim 15, which upon execution by the computer,further cause the computer to implement operations comprising: calculatethe position of the focus ring on the pick based on changes in thesensor outputs of the position detection sensors while the focus ring ismoved toward the station.